Heat treatment of magnetic parts



April 17, 1934. A. A. MEYER HEAT TREATMENT OF MAGNETIC PARTS Original Filed o t. 19, 1931 Patented Apr. 17, 1934 (11 111151) STATES 1,955,141 I near rasanmsr or moss-no mars Arthur Warner .Electrlc Brake Albert Meyer, nelcitowla,

amlgnor to rporation, 8outh Belo'it, Ill, a corporation of Illinois Application mm 19, 19:1, Sel'il No. 569,742 Renewed September 7, 1933 6 Claim!- (Cl. 115-21) This invention relates to the heat treatment of magnetic parts and more particularly to the treatment of parts to be used in magnetic friction devices.

I Friction clutches commonly comprise a magnet and an armature having'flat friction surfaces adapted to be brought into gripping engagement upon the energization of an annular winding enclosed by the two rings. Even after careful an- 10 nealing to remove the mechanical stresses, the engaging faces of such rings become distorted readily due to the shocks to which the rings are 7 subjected in handling, in grinding of their coacting faces, or in service use. Such detrimental characteristic is particularly aggravated in the case of the armature ring and renders uncertain the degree of gripping engagement which is capable of being developed when the magnet is err-'- ergized.

The primary object of the present invention is to provide a new and improved process for overcoming the above objection and for improving the magnetic properties of magnetic friction rings.

In the accompanying drawing, which illustrates an apparatus for carrying out the improved process, the numeral 1 indicates a flat armaturering composed of magnetic material and adapted for use in conjunction with a magnet havinga core 2 of U-shaped cross-section providing two concentric poles 3 between which is disposed a winding 4. The armature thus bridges the gap between the faces of the poles thereby forming with the magnets closed magnetic'circuit around the winding 4 so that a high flux density will exist in the magnetic parts when the winding is ener- .gizedbytheclosureofaswitch5inthecircuit including a winding and a battery 6.

The present invention contemplates the removal of mechanical strains in the armature and 40 normalization of the iron magneticallyby cool-' ing the iron through its critical temperature range while being subjected to magnetic flux at.

high density. Accordingly, the armature ring is first brought to a bright red heat. While at this temperature, the ring is placed against the face of the magnet so as to overlie both of the poles 3. Current is maintainedilowing in the windingdiwhiletheringiscoolingtoapoint substantially below the critical range of the iron. Finally the friction face of the ring is ground oil to the desired flatness.

By thus subjecting the armature ring to the action of magnetic flux while cooling through its 1 critical range, the iron is effectually normalized magnetically as well'as mechanically thereby effectually eliminating any tendency toward distortion of the friction face under shocks or other mechanical strains. It is contemplated that a as magnetic core may be normalized in a similar way by using the core as an armature for a magnet constructed as above described.

I claim as my invention:

1. The process of treating a magnetic ring for use in a magnetic friction device consisting in heating the ring to a temperature above its critical range, cooling the ring through said range, and passing magnetic flux through the ring while thus cooling. V

2. The process of treating a magnetic ring for I use in a magnetic friction device consisting in heating the ring to a temperature above its critical range, placing the heated ring on a magnet having a ferromagnetic circuit closed by the ring, so 1 and maintaining said magnet energized during cooling of the ring.

3. The process of normalizing a magnetic part which includes the step of annealing the part in a strong magnetic field.

4. For preventing surface distortion in the use of a friction element composed substantially of magnetic material, the process of normalizing said element which includes the step of annealing the element in a magnetic field.

5. The process of normalizing a friction element composed substantially of magnetic material and having a substantially flat friction sur-- face, said process comprising heating said part to a temperature above the critical range of said material and subjecting the material to magnetic flux while cooling.

6. The process-of normalizing a part composed of magnetic material which comprises heating the part and allowing the same to cool in a magnetic field.

ARTHUR ALBERT MEYER. 

